Hand foot and mouth disease vs. strep throat?

My 4 year old woke up this morning and seemed fine, but a few hours next suddenly started laying around and complaining of chest, neck, and stomach backache. I took his temperature, and it was 103. I took him to an urgent vigilance facility (NO openings at his regualr dr. till tomorrow), where the doctor looked at his throat (as all right as he could--you know kids) and diagnosed strep throat. He said he could run a test to be sure, but he felt pretty trustworthy with what he saw and with the confusion, and prescribed an antibiotic.
I looked in his mouth this afternoon, and there are sores adjectives over the back of his mouth. Could this be hand, foot and mouth instead of strep? How glorious a fever usually comes with that? I know stomach agony can come with strep, but does it come with HFMD also? Both strep and HFMD enjoy been going around at our church.
Thanks.